29 Questions
Which thyroid hormone is significantly less biologically active than T3?
T4 (Thyroxine)
What does T3 stand for regarding thyroid function?
Triiodothyronine
Which thyroid hormone has a longer half-life, according to the text?
T3 (Triiodothyronine)
Which hormone stimulates the thyroid gland to secrete T4 and T3?
Thyroid stimulating hormone
In hypothyroidism, which of the following levels is typically elevated?
TSH (Thyroid stimulating hormone)
Which enzyme attacked in Hashimoto's Disease is crucial for producing thyroid hormones?
Thyroid peroxidase enzyme
What is a common symptom of hypothyroidism related to the skeletal muscles?
Muscle aches/stiffness
Which of the following is NOT a common sign/symptom of hypothyroidism?
Warm, flushed skin
What is a typical laboratory finding in individuals with hypothyroidism?
Elevated thyroid-stimulating hormone (TSH)
Which group should receive thyroid replacement therapy (TRT) to improve their condition?
Individuals displaying neurological deficits
What is a goal of thyroid replacement therapy (TRT) in hypothyroid patients?
Provide symptomatic relief
What is the role of TRH in the regulation of thyroid hormones?
Instructs the pituitary gland to release TSH
Which gland is responsible for detecting low levels of thyroid hormones in the body?
Hypothalamus
In primary hypothyroidism, what happens to TSH levels?
They increase
How does the hypothalamus respond to persistently low levels of thyroid hormones?
It secretes TRH
What is the effect of elevated levels of thyroid hormones on TRH secretion?
TRH secretion decreases
Why does TSH levels remain low in hyperthyroidism?
Pituitary gland stops releasing TSH
How long does it typically take for symptoms to lessen after starting thyroid treatment?
2-3 weeks
When should TSH and FT4 levels be monitored after initiating thyroid treatment?
6-8 weeks
What is the recommended monitoring frequency once TSH levels are within the normal range?
Yearly
If a patient becomes pregnant while on thyroid medication, what may be required?
Taking 2 extra tabs per week
How should thyroid medication be taken to ensure optimal absorption?
On an empty stomach
What is the recommended action if signs of hyperthyroidism are observed while on thyroid hormone replacement?
Seek medical advice to adjust the dose
What is the rationale for combining T4 with T3 in hypothyroid patients with normalized TSH but persistent symptoms?
To provide a more potent replacement of T3
Based on the guidelines provided, what is the daily replacement dose of Levothyroxine (Synthroid®) for adults ≥ 61 years of age without evidence of cardiac disease?
25 to 50 mcg once daily
What is the recommended time to take synthetic T4 replacement medication according to the text?
60 minutes before breakfast or 3 hours after dinner
What is the target range for TSH levels in patients receiving synthetic T4 replacement therapy?
0.4 to 4 mIU/L
How often should the dose of synthetic T4 replacement be adjusted if needed?
At 6- or 8-week intervals
What is the purpose of looking for hyperthyroid symptoms in hypothyroid patients during replacement therapy?
To avoid overreplacement
Study Notes
Thyroid Gland Functions
- Thyroid gland secretes thyroid hormones (THs) independently, producing more T4 (Thyroxine) than T3 (Triiodothyronine) into circulation.
- T4 is solely produced by the thyroid gland and is less biologically active than T3.
- T3 is more biologically active than T4 and has a half-life of 1 day.
Thyroid Hormone Conversion
- T4 is converted to T3 in peripheral tissues.
Thyroid Function Tests (TFTs)
- TFTs measure Free T4 (FT4) and Thyroid-Stimulating Hormone (TSH) levels.
- Normal FT4 levels: 0.8-2.7 ng/dL.
- Normal TSH levels: 0.5-4.7 mIU/L.
Hypothyroidism
- Condition characterized by decreased thyroid gland activity and compensatory increase in TSH.
- Primary hypothyroidism can be caused by Hashimoto's Disease, which involves antibodies attacking the thyroid gland.
Signs and Symptoms of Hypothyroidism
- Dry, thin, cool, coarse skin and hair.
- Diffuse alopecia.
- Puffy face, hands, and feet.
- Brittle nails.
- Cool peripheral extremities.
- Slowed reflexes and speech.
- Bradycardia.
- Weight gain with poor appetite.
- Tiredness, weakness, and low energy level.
- Memory impairment.
- Muscle aches and stiffness.
- Carpal tunnel syndrome.
- Cold intolerance.
- Hoarseness.
- Constipation.
- Menstrual irregularities.
- Gradual onset of symptoms.
Diagnosis of Hypothyroidism
- Signs and symptoms.
- Lab tests: low FT4 and high TSH.
- Positive TPO antibodies.
Goals of Thyroid Replacement Therapy (TRT)
- Restore thyroid hormone levels within tissues.
- Provide symptomatic relief.
- Prevent neurologic deficits in newborns and children.
- Normalize labs.
Who Should be Treated?
- Patients with TSH > 11 mIU/L.
Thyroid Replacement Therapy (TRT)
- Restore thyroid hormone levels within tissues.
- Use synthetic thyroid hormone (T4) Levothyroxine (Synthroid).
- Dosing: 1.6 mcg/kg/day IBW for adults ≤60 years old without cardiac disease.
- Dosing: 25-50 mcg once daily for adults ≥ 61 years old without cardiac disease.
- Dosing: 12.5-25 mcg/day and titrate up based on tolerability for patients with cardiac disease or TSH 5-10 mIU/L.
- Monitor TSH and FT4 levels ≥ 6 weeks after initiation or any dose adjustments.
- Treatment is lifelong.
Test your knowledge on the function of the thyroid gland and how it regulates the body's physiological functions. This quiz covers the relationship between TSH, FT4, TRH, and how they interact to maintain hormonal balance.
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